iommu/arm-smmu-v3: Remove arm_smmu_master->domain

Introducing global statics which are of type struct iommu_domain, not
struct arm_smmu_domain makes it difficult to retain
arm_smmu_master->domain, as it can no longer point to an IDENTITY or
BLOCKED domain.

The only place that uses the value is arm_smmu_detach_dev(). Change things
to work like other drivers and call iommu_get_domain_for_dev() to obtain
the current domain.

The master->domain is subtly protecting the master->domain_head against
being unused as only PAGING domains will set master->domain and only
paging domains use the master->domain_head. To make it simple keep the
master->domain_head initialized so that the list_del() logic just does
nothing for attached non-PAGING domains.

Tested-by: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
Tested-by: Nicolin Chen <nicolinc@nvidia.com>
Tested-by: Moritz Fischer <moritzf@google.com>
Reviewed-by: Nicolin Chen <nicolinc@nvidia.com>
Reviewed-by: Mostafa Saleh <smostafa@google.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/10-v6-96275f25c39d+2d4-smmuv3_newapi_p1_jgg@nvidia.com
Signed-off-by: Will Deacon <will@kernel.org>

drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c

@@ -2507,19 +2507,20 @@ static void arm_smmu_disable_pasid(struct arm_smmu_master *master)
 
 static void arm_smmu_detach_dev(struct arm_smmu_master *master)
 {
+	struct iommu_domain *domain = iommu_get_domain_for_dev(master->dev);
+	struct arm_smmu_domain *smmu_domain;
 	unsigned long flags;
-	struct arm_smmu_domain *smmu_domain = master->domain;
 
-	if (!smmu_domain)
+	if (!domain)
 		return;
 
+	smmu_domain = to_smmu_domain(domain);
 	arm_smmu_disable_ats(master, smmu_domain);
 
 	spin_lock_irqsave(&smmu_domain->devices_lock, flags);
-	list_del(&master->domain_head);
+	list_del_init(&master->domain_head);
 	spin_unlock_irqrestore(&smmu_domain->devices_lock, flags);
 
-	master->domain = NULL;
 	master->ats_enabled = false;
 }
 
@@ -2573,8 +2574,6 @@ static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev)
 
 	arm_smmu_detach_dev(master);
 
-	master->domain = smmu_domain;
-
 	/*
 	 * The SMMU does not support enabling ATS with bypass. When the STE is
 	 * in bypass (STE.Config[2:0] == 0b100), ATS Translation Requests and
@@ -2593,28 +2592,22 @@ static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev)
 	case ARM_SMMU_DOMAIN_S1:
 		if (!master->cd_table.cdtab) {
 			ret = arm_smmu_alloc_cd_tables(master);
-			if (ret) {
-				master->domain = NULL;
+			if (ret)
 				goto out_list_del;
-			}
 		} else {
 			/*
 			 * arm_smmu_write_ctx_desc() relies on the entry being
 			 * invalid to work, clear any existing entry.
 			 */
 			ret = arm_smmu_write_ctx_desc(master, IOMMU_NO_PASID,
 						      NULL);
-			if (ret) {
-				master->domain = NULL;
+			if (ret)
 				goto out_list_del;
-			}
 		}
 
 		ret = arm_smmu_write_ctx_desc(master, IOMMU_NO_PASID, &smmu_domain->cd);
-		if (ret) {
-			master->domain = NULL;
+		if (ret)
 			goto out_list_del;
-		}
 
 		arm_smmu_make_cdtable_ste(&target, master);
 		arm_smmu_install_ste_for_dev(master, &target);
@@ -2640,7 +2633,7 @@ static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev)
 
 out_list_del:
 	spin_lock_irqsave(&smmu_domain->devices_lock, flags);
-	list_del(&master->domain_head);
+	list_del_init(&master->domain_head);
 	spin_unlock_irqrestore(&smmu_domain->devices_lock, flags);
 
 out_unlock:
@@ -2841,6 +2834,7 @@ static struct iommu_device *arm_smmu_probe_device(struct device *dev)
 	master->dev = dev;
 	master->smmu = smmu;
 	INIT_LIST_HEAD(&master->bonds);
+	INIT_LIST_HEAD(&master->domain_head);
 	dev_iommu_priv_set(dev, master);
 
 	ret = arm_smmu_insert_master(smmu, master);

drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h

@@ -695,7 +695,6 @@ struct arm_smmu_stream {
 struct arm_smmu_master {
 	struct arm_smmu_device		*smmu;
 	struct device			*dev;
-	struct arm_smmu_domain		*domain;
 	struct list_head		domain_head;
 	struct arm_smmu_stream		*streams;
 	/* Locked by the iommu core using the group mutex */